- Family Gelidaceae
- Gelidium amansii, G. corneum
- Agar-Agar, Agar Weed, Japanese/Chinese Isinglass, Red Algae
- None listed
This perennial seaweed grows up to three feet long, comprising of reddish-brown, translucent, multibranched ribbons and fronds, called thalli (singular thallus), that sprout from a permanent base every year. The thallus is cylindrical or flattened, subdivided, and tough. The plant produces spherical fruit late in the autumn or early winter. Indigenous to the Pacific coasts of Japan and China, Sri Lanka, it also grows along the South African coasts to a depth of 100 feet below sea level.
Commercial harvesters rake the plants from the banks and rocks. The refining of it is a complex process. After cleaning, it is boiled with sulphuric acid, which yields agar, a thick gummy liquid. This is set to form a jelly, which is colorless and tasteless and capable of absorbing 200 times its volume of water. The final product is cut into thin strips, dried, and stored in a cool place to prevent the growth of mold. The strips are then ground into a fine powder. About 6,500 tons of agar are processed each year.
Agar is a common food thickening agent, but it is used mostly in scientific research as a culture medium for growing micro-organisms in petri dishes.
The Japanese name kanten means “cold weather,” referring to the fact that the seaweed is harvested in the winter months. Freezing and thawing are necessary for the manufacturing process.
- bulk laxative
- polysaccharides (mainly agarose and agaropectine [up to 90%])
- The gelatinous extract, known as Agar
- The polysaccharides are very mucilaginous, making it a good bulk laxative.
Like most seaweeds and their derivatives, agar is nutritious, containing large amounts of mucilage which absorbs water in the intestines and swells. This stimulates bowel activity, without purging, causing the subsequent elimination of feces.
The powder is used to make a jelly that is given to the sick and infirm for its highly digestible protein.
Although G. amansii is the main agar-producing species, there are other closely related species found around the world used as alternative sources. One is G. cartilagineum, found on the Pacific coast of North America.